Young Leslie Morton gazed out across the waves but heavy fog prevented him from making out the Cork coast. Suddenly, the 18-year-old ship-hand, on board the Lusitania ocean liner, noticed a trail of bubbles 500 metres away. They were quickly approaching the British-registered ship.

He grabbed the megaphone and shouted to the bridge "Torpedoes coming on the starboard side" but his warning cries were too late.

It was the afternoon of May 7, 1915, when the Lusitania, en route to Liverpool from New York, sank just 11 miles off the Old Head of Kinsale with the cold Atlantic waters claiming 1,198 lives, including almost 100 children.

A German U-boat, lying in wait, had fired on the ocean liner.

In the town of Cobh -- then Queenstown -- distress signals were received. Vice Admiral Sir Charles Coke gathered up whatever ships were available and told their captains to sail towards the sinking Lusitania.

They arrived two hours after the ship sank to the depths of the ocean floor. When they got there, they picked up any people still alive in the water and six lifeboats. In the days that followed, locals helped bury the dead and comfort the 768 survivors. As bodies and wreckage started to wash up on the coast, rumours quickly spread that the vessel was targeted because it was carrying explosives to be used in the war effort against German forces.

If this was the case, then the ship would have been considered a legitimate target.

Now though, new evidence -- discovered by a team of American scientists -- has revealed that the RMS Lusitania did not contain a secret cargo of high explosives.

The sinking brought America into World War I and conspiracy theorists believe Winston Churchill, then Lord Admiral, had prior knowledge of the impending danger from U-boat attack off the Irish coast and may have allowed the ship to be sacrificed for that very end.

British officials have always been evasive about the presence of munitions on the Lusitania. Two cargo manifests were submitted; the second, filed after the ship sailed, indicated there were light munitions on board.

Some had believed the ship was carrying much more, however, and that the British Navy attempted to destroy the wreck in the 1950s to conceal its military cargo.

It was claimed the explosives were stowed away on board, concealed as cheese or casks of beef on the ship's cargo manifest.

The new scientific research, which included a search of the shipwreck as well as laboratory tests and a computer reconstruction of the sinking, has cleared the British government of the charges against it.

The original investigations into the precise causes of the ship's loss were obstructed by the need for wartime secrecy and a propaganda campaign to ensure all blame fell on Germany.

Now, though, scientists say they have been able to study the wreckage in close detail and have found no evidence to support the conspiracy claims.

They also concluded that the second explosion, reported by survivors, was caused by one of the ship's boilers exploding and not something more sinister.

A series of dives to the wreck using a miniature submarine was conducted by the research team as well as additional tests at the Lawrence Livermore National Laboratory in California -- a US government-funded research facility specialising in explosives.

In a series of controlled explosions and tests, they say they proved that aluminum, used in landmine construction, was not the main ingredient in the second explosion that eventually sank the ship.

The expedition and experiments were filmed by National Geographic for a special documentary to be aired tomorrow -- 105 years to the day from when the RMS Lusitania first took to the waters as a passenger ocean liner on August 26, 1907.

Dark Secrets of the Lusitania will air on the National Geographic channel at 7pm tomorrow.